A method for preparing carbon nanotubes, carbon nanotubes and applications

Abstract

The present application relates to a kind of preparation technology of carbon nanotube and its application, including the following steps: first, binary aromatic amine is diazotized to obtain acidic diazonium salt solution;Anionic regenerated cellulose is dynamically immersed in the diazonium salt solution of binary aromatic amine at room temperature;The cellulose regenerated fiber treated by the above steps is drawn and dynamically immersed in sodium hydroxide or sodium acetate aqueous solution;The cellulose regenerated fiber treated by the above steps is drawn into the red-hot iron pipe above 700 DEG C;Then the obtained carbon nanotube is washed, dried, drawn, oiled;Finally, the finished product super-long carbon nanotube is obtained by winding into a roll.The whole preparation process is continuous, and the process is simple, low cost, high yield, high production efficiency, and the carbon nanotube has single conductive property, without subsequent separation, in addition, fibers can exist independently, and will not affect the use effect because of agglomeration together.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high-performance fibers, and particularly relates to a preparation technology of super-long carbon nanotubes and application thereof. BACKGROUND

[0002] Carbon nanotubes are coaxial circular tubes composed of carbon atoms arranged in a hexagonal pattern, from single-layer to multi-layer, with small density, large length-diameter ratio, stable existence and certain rigidity. The unique structure determines that it has very excellent physical (mechanical, electrical, optical, thermal, etc.) and chemical properties. Carbon nanotubes are composed of C-C covalent bonds formed by sp 2 hybridization, with few defects. Theoretical calculations and experimental results show that the composition of σ bond between C-C makes the tensile strength of carbon nanotubes as high as 100 GPa, about 50 times that of steel, and the elongation at break is as high as 15%-20%. The Young's modulus of carbon nanotubes with perfect structure is as high as 1 TPa, about 5 times that of steel. These performances are far higher than those of any other materials at present. Carbon nanotube fibers are emerging high-tech special fiber materials, with advantages of high strength, high modulus, small density, high toughness, high temperature resistance, corrosion resistance, long service life, strong designability, etc. They have wide application in the fields of composite materials, aerospace, power cables, batteries, energy storage and conversion, electronic information technology, electronic devices, biological medicine, catalysis and environmental science. However, the carbon nanotubes prepared by the current preparation technology are generally short, with length of hundreds of nanometers to several microns, and the longest is several tens of centimeters. Therefore, there is a huge gap between the actual performance of carbon nanotube fibers prepared by the carbon nanotubes prepared at present and the theoretical performance of carbon nanotubes. SUMMARY

[0003] In order to enable carbon nanotubes to exert their inherent performance, the present application provides a preparation method of super-long carbon nanotubes and application thereof. The super-long carbon nanotubes prepared by the present application can be directly used as fibers without spinning.

[0004] The technical scheme of the present application is as follows:

[0005] In a first aspect, the present application provides a preparation method of super-long carbon nanotubes, characterized by comprising the following steps:

[0006] Step (1): diazotization reaction of binary aromatic amine to obtain an acidic diazonium salt solution;

[0007] Step (2): dynamic immersion of a straight forward moving anionic regenerated cellulose fiber in the binary aromatic amine diazonium salt solution obtained in step (1), and continue to move forward after immersion. The temperature of the binary aromatic amine diazonium salt solution is lower than 60℃, and the mass concentration of the solution is lower than 90%.

[0008] Step (3): the cellulose regenerated fiber treated in step (2) is introduced into and immersed in an aqueous solution of sodium hydroxide or sodium acetate, and after the immersion is completed, the cellulose regenerated fiber continues to move forward, the temperature of the solution of sodium hydroxide or sodium acetate is 10-100℃, and the mass concentration of the solution is less than 95%;

[0009] Step (4): the cellulose regenerated fiber treated in step (3) is introduced into a red-hot iron pipe with a temperature of more than 700℃ to obtain carbon nanotubes, and the heat treatment time is less than 3 hours.

[0010] Step (5): the carbon nanotubes obtained in step (4) are washed, dried, drawn, oiled, and finally collected into a roll to obtain finished product super-long carbon nanotubes.

[0011] In step (1), the binary aromatic amine is one or more of p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, and biphenyldiamine.

[0012] In step (2), the diameter of the anionic cellulose regenerated fiber is 1-1000nm, and the preparation method can be that the cellulose regenerated fiber is first prepared, and then the surface of the cellulose regenerated fiber is chemically modified to make the cellulose molecules on the fiber surface into carboxymethyl cellulose, sulfonated ethyl cellulose, and polyanionic cellulose; or the anionic cellulose regenerated fiber can be directly obtained by directly spinning carboxymethyl cellulose, sulfonated ethyl cellulose, and polyanionic cellulose as raw materials. In any case, the finished product anionic cellulose regenerated fiber has negative charges uniformly distributed on the surface, which ensures that the double nitrogen salt of the binary aromatic amine is uniformly adsorbed on the surface of the anionic cellulose regenerated fiber.

[0013] In step (2), the anionic cellulose regenerated fiber is continuously and dynamically introduced into and immersed in the double nitrogen salt solution of the binary aromatic amine, and the double nitrogen salt solution of the binary aromatic amine is uniformly treated by ultrasonic waves and the like; and the solution is continuously supplemented, and the supplementing method is to prepare the double nitrogen salt solution on site, and when the original solution is about to be consumed, the newly prepared solution is added, which ensures that the subsequent double nitrogen salt is uniformly and completely covered on the surface of the cellulose regenerated fiber, that is, the fiber surface is uniformly and completely covered with the double nitrogen salt of the binary aromatic amine after the immersion is completed.

[0014] In step (2), the time for which the negatively charged cellulose regenerated fiber is dynamically immersed in the double nitrogen salt solution of the binary aromatic amine obtained in step (1) is 0.01-120 minutes. The mass ratio of the negatively charged cellulose regenerated fiber to the double nitrogen salt of the binary aromatic amine is 0.001:1-1000:1.

[0015] In step (3), the cellulose regenerated fiber treated in step (2) is moved forward into and immersed in the aqueous solution of sodium hydroxide or sodium acetate for 0.01-120 minutes; the molar ratio of sodium hydroxide or sodium acetate to the double nitrogen salt of the binary aromatic amine is 0.5:1-500:1; the sodium hydroxide or sodium acetate solution is treated by ultrasonic wave or the like to ensure the uniformity of the solution, and the sodium hydroxide or sodium acetate solution is replaced with a new solution when the sodium hydroxide or sodium acetate is about to be consumed, so that the coupling reaction between the double nitrogen salt molecules of the binary aromatic amine can continuously occur; after the reaction in this step, the coupling reaction between the double nitrogen salt molecules of the binary aromatic amine generates the biaromatic hydrocarbon, and the surface of the anionic cellulose regenerated fiber is completely and uniformly covered with the biphenyl aromatic hydrocarbon, which is the precursor of the carbon nanotube structure, that is, the structure of the carbon nanotube has been initially formed, and most of the covalent bonds between the benzene rings have been formed, leaving only a small amount of unreacted C-H dangling bonds.

[0016] In step (4), the cross section of the iron pipe can be circular, square, rectangular, etc., which can be flexibly selected according to actual needs; the iron pipe is placed in a protective cover, a plurality of exhaust holes are arranged on the protective cover, and inert gas is passed through the protective cover; after this step, the negatively charged cellulose regenerated fiber is carbonized, the unreacted C-H dangling bonds between the benzene rings on the fiber surface are pyrolyzed to connect the benzene rings together, and a closed six-membered ring is formed between the benzene rings, that is, the cellulose regenerated fiber disappears in this step, and the structure of the carbon nanotube has been completely formed, and the obtained product is an ultralong carbon nanotube.

[0017] In step (5), the washing is water washing by using clean water to remove the residual ash and inorganic salt contained in the carbon nanotube;

[0018] In step (5), the purpose of drying is to remove the moisture on the surface and inside of the carbon nanotube, and the drying can be performed by using a hot roller, a hot air drying box or the like;

[0019] In step (5), the drafting can be positive drafting or negative drafting, and the drafting multiple is controlled to be 0.1-10;

[0020] In step (5), the purpose of oiling is to form a protective film on the outside of the carbon nanotube, so as to reduce the damage caused by the friction with the outside.

[0021] Finally, the diameter of the obtained ultralong carbon nanotube is 1-1000 nm.

[0022] In a second aspect of the present application, the ultralong carbon nanotube prepared by the preparation method is provided.

[0023] The third aspect of the present application provides the application of the ultra-long carbon nanotubes prepared by the preparation method, including the fields of composite materials, aerospace, power cable, battery, energy storage and conversion, electronic information technology, electronic device, biological medicine, catalysis and environmental science, etc. In addition, a plurality of single carbon nanotubes can be combined into a carbon nanotube filament with a certain diameter, and the carbon nanotube filament can be processed into a chopped fiber according to needs, and then the chopped fiber is used to manufacture a carbon nanotube cloth or a carbon nanotube paper.

[0024] The present application has the advantages that: the ultra-long carbon nanotubes are prepared by using the ultra-long anionic regenerated cellulose fiber as a template, the whole process is simple and easy to implement, the length of the prepared carbon nanotubes can reach meters or even kilometers or ten kilometers, which is much larger than the length of the carbon nanotubes prepared by the commonly used methods at present, and most of the carbon nanotubes prepared at present are nanoscale or micrometer scale.

[0025] The present application has the advantages that: because the ultra-long carbon nanotubes are prepared by using the ultra-long anionic regenerated cellulose fiber as a template, the ultra-long carbon nanotubes with various diameters can be prepared flexibly by controlling the diameter of the ultra-long anionic regenerated cellulose fiber according to needs.

[0026] The present application has the advantages that: as known by those skilled in the art, one of the commonly used methods for preparing carbon nanotubes at present is the chemical vapor deposition method, which uses a nanoscale catalyst in the preparation of carbon nanotubes, and the catalyst is easy to remain in the carbon nanotubes after the preparation is completed, which affects the purity of the carbon nanotubes and further affects the use effect; the present application does not use a nanoscale catalyst throughout the whole process, there is no case of catalyst remaining in the carbon nanotubes, the ash generated after carbonization can be cleaned in the subsequent cleaning process, and will not remain in the carbon nanotube fibers, so it will not affect the purity of the carbon nanotubes, nor will it affect the use effect.

[0027] The present application has the advantages that: as known by those skilled in the art, the carbon nanotubes prepared by the commonly used methods for preparing carbon nanotubes at present have both metallic tubes and semiconductor tubes, and the carbon nanotubes with one kind of conductive property are removed and only the carbon nanotubes with the required conductive property are retained according to the different needs of the application fields, which not only increases the product cost, but also further increases the process complexity of the product and reduces the production efficiency; the carbon nanotubes prepared by the present application have a single conductive property, and do not need to be separated subsequently.

[0028] The advantage of the present application: as known by those skilled in the art, the carbon nanotubes prepared at present are short in size (most of them are nanometer level, micrometer level), so the surface energy is extremely high, and they are very easy to gather together, if the carbon nanotubes cannot be uniformly dispersed, then the use effect will be greatly negatively affected, at present, the covalent modification or non-covalent modification is generally adopted on the finished carbon nanotubes to improve the dispersibility, which undoubtedly increases the cost; in the present application, the length of the super-long carbon nanotubes generated after the reaction reaches the meter level or even kilometer level or ten-thousand-meter level, the carbon nanotubes can exist independently, and are independently wound into silk cylinders, so there is no problem of mutual gathering together to affect the use effect. Of course, several carbon nanotubes can also be combined into a carbon nanotube filament bundle according to the needs.

[0029] The advantage of the present application: the carbon nanotube fibers prepared at present are spun from carbon nanotubes which are short in size, and the tensile strength is only several GPa, which is only at the strength level of ordinary aramid fiber and carbon fiber; while the technology of the present application can prepare super-long carbon nanotubes at one time, and the tensile strength is much higher than that of the carbon nanotube fibers spun at present, and the tensile strength can even be as high as several tens of GPa.

[0030] The advantage of the present application: the commonly used methods for preparing carbon nanotubes at present generally have the problems of complex process, expensive equipment, high cost and low yield, the present application is to synthesize super-long carbon nanotubes by using chemical method, the whole preparation process is dynamic and continuous, the process is simple and easy to operate, the cost is low, the yield is high, and the production efficiency is high. BRIEF DESCRIPTION OF DRAWINGS

[0031] The above and other features of the present application will be more fully understood when considered in connection with the following detailed description in conjunction with the accompanying drawings, in which: Figure One The above and other features of the present application will be more fully understood when considered in connection with the following detailed description in conjunction with the accompanying drawings, in which:

[0032] Figure 1 The flow chart for preparing the carbon nanotubes of the present application. DETAILED DESCRIPTION

[0033] The following examples are described to assist in the understanding of the present application, and the examples are not and should not be interpreted as limiting the protection scope of the present application in any way.

[0034] Example 1:

[0035] Example 1

[0036] First, 2 grams of m-phenylenediamine is dissolved in 35 grams of 10% hydrochloric acid solution, and the mixture is stirred to keep the temperature at -5°C. Then, 21.5 grams of 10% sodium nitrite solution is gradually added to the mixture under stirring for 1.5 hours to obtain a diazonium salt solution of m-phenylenediamine.

[0037] 0.3 grams of anionic cellulose fibers with a diameter of 5 nanometers are dynamically immersed in the above solution for 15 minutes. The fibers are continuously moved forward before, during and after the immersion.

[0038] The above diazonium salt-impregnated cellulose fibers are continuously and dynamically introduced into and immersed in 25 grams of an aqueous sodium hydroxide solution, the immersion time is 15 minutes, the solution temperature is 75°C, and the mass concentration of the sodium hydroxide solution is 62%. At this time, the coupling reaction between the diazonium salt molecules of the diarylamine occurs to form biphenyl aromatic hydrocarbons, the surface of the anionic cellulose fibers is completely covered with biphenyl aromatic hydrocarbons, the structure of the carbon nanotube has been initially formed, and most of the covalent bonds between the benzene rings have been formed, leaving only a small amount of unreacted C-H dangling bonds.

[0039] The above anionic cellulose fibers completely covered with biphenyl aromatic hydrocarbons are dynamically introduced into a 800°C red-hot iron pipe with a protective cover for heat treatment, the heat treatment time is 30 minutes and the heat treatment is carried out under nitrogen protection, to achieve the following two purposes: 1) carbonization of the anionic cellulose fibers; 2) thermal decomposition of the unreacted C-H dangling bonds between the benzene rings to connect the benzene rings together, forming a closed six-membered ring between the benzene rings. After this step, the cellulose fibers disappear, the structure of the carbon nanotube has been completely formed, and the super-long carbon nanotube is obtained.

[0040] The super-long carbon nanotube obtained by the above steps is washed with water to remove residual ash and inorganic salts contained in the interior and surface of the carbon nanotube, and the water-washed carbon nanotube is dried in a hot air drying oven. The carbon nanotube is cooled and finished with oil, and finally the finished super-long carbon nanotube is obtained by winding the fibers.

[0041] The diameter of the finished super-long carbon nanotube is about 5 nanometers.

[0042] The tensile strength of the finished super-long carbon nanotube is 12 GPa, and the tensile modulus is 512 GPa.

[0043] Although several aspects and embodiments have been disclosed in this application, other aspects and embodiments will be apparent to those skilled in the art from the disclosure herein. The aspects and embodiments disclosed in this application are intended to be illustrative only and the true scope of the application will be determined by the following claims appropriately interpreted in accordance with the Patent Statutes, including equivalents.

Claims

1. A method for preparing carbon nanotubes, the whole process being dynamic and continuous, comprising the following steps: Step (1): diazotization of a binary aromatic amine to obtain a double diazonium salt solution of acid; Step (2): dynamic immersion of an anionic regenerated cellulose fiber moving forward in the double diazonium salt solution of binary aromatic amine obtained in Step (1), and the fiber continues to move forward after the immersion is completed, the temperature of the double diazonium salt solution of binary aromatic amine is lower than 60℃, and the mass concentration of the solution is lower than 90%; Step (3): leading the regenerated cellulose fiber treated in Step (2) to be dynamically immersed in an aqueous solution of sodium hydroxide or sodium acetate, and the fiber continues to move forward after the immersion is completed, the temperature of the solution of sodium hydroxide or sodium acetate is 10-100℃, and the mass concentration of the solution is lower than 95%; Step (4): leading the regenerated cellulose fiber treated in Step (3) to be heat treated by a red-hot iron pipe above 700℃ to obtain carbon nanotubes, and the heat treatment time is less than 3 hours; and Step (5): washing, drying, drawing and oiling the carbon nanotubes obtained in Step (4), and finally collecting the carbon nanotubes to obtain finished product super-long carbon nanotubes. In Step (1), the binary aromatic amine is one or more of p-phenylenediamine, m-phenylenediamine, o-phenylenediamine and biphenyldiamine. In Step (2), the diameter of the anionic regenerated cellulose fiber ranges from 1 to 1000 nm, and the method for preparing the anionic regenerated cellulose fiber is to first prepare a regenerated cellulose fiber, and then perform chemical modification on the surface of the regenerated cellulose fiber to make the cellulose molecules on the fiber surface generate carboxymethyl cellulose, sulfonic acid ethyl cellulose and polyanionic cellulose; or directly use carboxymethyl cellulose, sulfonic acid ethyl cellulose and polyanionic cellulose as raw materials to spin to directly obtain the anionic regenerated cellulose fiber. In any case, the finished product anionic regenerated cellulose fiber has negative charges uniformly distributed on the surface thereof, which can ensure that the double diazonium salt of the binary aromatic amine is uniformly adsorbed on the surface of the anionic regenerated cellulose fiber. In Step (2), the anionic regenerated cellulose fiber is continuously and dynamically immersed in the double diazonium salt solution of binary aromatic amine, and the uniformity of the solution is ensured by ultrasonic treatment. In addition, the solution is continuously supplemented, and the supplementing method is to prepare the double diazonium salt solution on site, and add the newly prepared solution when the original solution is about to be consumed. In this way, it can be ensured that the subsequent double diazonium salt is uniformly and fully covered on the surface of the regenerated cellulose fiber, that is, the fiber surface is uniformly and completely covered with the double diazonium salt of binary aromatic amine after the immersion is completed. In Step (2), the time for which the anionic regenerated cellulose fiber is dynamically immersed in the double diazonium salt solution of binary aromatic amine obtained in Step (1) is 0.01-120 minutes, and the mass ratio of the anionic regenerated cellulose fiber to the double diazonium salt of binary aromatic amine is: ​ 2. The method of claim 1, wherein the carbon nanotubes are produced by the method of claim 1. ​ 3. The method of claim 1, wherein the carbon nanotubes are grown on the substrate by a chemical vapor deposition method. ​ 4. The method of claim 1, wherein the carbon nanotubes are grown on the substrate by a chemical vapor deposition method. ​ 5. The method for preparing carbon nanotubes as described in claim 1, characterized in that, ​ 0.001:1-1000:1。 6. The method of claim 1, wherein the carbon nanotubes are grown on the substrate by a chemical vapor deposition method. In step (3), the cellulose regenerated fiber treated in step (2) is moved forward and immersed in the aqueous solution of sodium hydroxide or sodium acetate for 0.01-120 minutes; the molar ratio of sodium hydroxide or sodium acetate to the double nitrogen salt of the binary aromatic amine is 0.5:1-500:1; the sodium hydroxide or sodium acetate solution is treated by ultrasonic waves to ensure uniformity, and the sodium hydroxide or sodium acetate solution is replaced with a new solution when the sodium hydroxide or sodium acetate is about to be consumed, to ensure that the coupling reaction between the double nitrogen salt molecules of the binary aromatic amine continues; after this step, the coupling reaction between the double nitrogen salt molecules of the binary aromatic amine generates biphenyl aromatic hydrocarbons, and the surface of the anionic cellulose regenerated fiber is completely covered with uniform biphenyl aromatic hydrocarbons, which are the precursors of carbon nanotube structures, that is, the structure of the carbon nanotube has been initially formed, and most of the covalent bonds between the benzene rings have been formed, leaving only a small amount of unreacted C-H dangling bonds.

7. The method of claim 1, wherein the carbon nanotubes are grown on the substrate by a chemical vapor deposition method. In step (4), the cross-sectional shape of the iron pipe is circular, square, or rectangular; the iron pipe is placed in a protective cover, the protective cover is provided with a plurality of exhaust holes, and inert gas is passed through the protective cover; after this step, the negatively charged cellulose regenerated fiber is carbonized, the C-H dangling bonds between the benzene rings on the fiber surface are pyrolyzed, and the benzene rings are connected together, forming a closed six-membered ring, that is, in this step, the cellulose regenerated fiber disappears, and the structure of the carbon nanotube has been completely formed, resulting in an ultralong carbon nanotube.

8. The method of claim 1, wherein the carbon nanotubes are grown on the substrate by a chemical vapor deposition process. In step (5), 1) washing is water washing with clean water to remove residual ash and inorganic salts contained in the interior and surface of the carbon nanotube; 2) the purpose of drying is to remove the moisture on the surface and inside of the carbon nanotube, and drying is performed using a hot roller or a hot air drying box; 3) drafting is positive drafting or negative drafting, and the drafting multiple is controlled to be between 0.1-10; 4) the purpose of oiling is to form a protective film on the outside of the carbon nanotube, thereby reducing damage caused by friction with the outside world.

9. The ultralong carbon nanotube prepared by the method of any one of claims 1-8, having a diameter of 1-1000 nm.

10. The application of the ultralong carbon nanotube of claim 9, including composite materials, aerospace, power cables, batteries, energy storage and conversion, electronic information technology, electronic devices, biomedicine, catalysis, and environmental science, in addition to combining several single carbon nanotubes into a carbon nanotube filament with a certain diameter, or processing the carbon nanotube filament into a chopped fiber, and then manufacturing a carbon nanotube cloth or a carbon nanotube paper from the chopped fiber.

Images